A reagent preparing apparatus for preparing a reagent by diluting an undiluted solution of the reagent by using a dilution liquid is conventionally known.
For instance, Japanese Laid-Open Patent Publication No. H1-167660 discloses a reagent preparing apparatus including a liquid amount measurement tube for holding a predetermined amount of concentrated solution, and a liquid amount measurement tank for holding a predetermined amount of pure water. The reagent preparing apparatus is configured to prepare the reagent by mixing the concentrated solution supplied from the liquid amount measurement tube and the pure water supplied from the liquid amount measurement tank.
U.S. Pat. No. 5,800,056 discloses a reagent preparing apparatus including a reagent tank for holding a predetermined amount of high concentration reagent, a pure water tank for holding a predetermined amount of pure water, a reagent preparing tank, and a pump for supplying pure water to the reagent preparing tank by a small amount at a time. The reagent preparing apparatus supplies the high concentration reagent from the reagent tank to the reagent preparing tank, and supplies the pure water from the pure water tank to the reagent preparing tank by an amount less than the amount necessary for diluting the high concentration reagent to the desired concentration. Thereafter, the reagent preparing apparatus supplies pure water by the pump to the reagent preparing tank by a small amount at a time to approach the reagent in the reagent preparing tank to the desired concentration. The high concentration reagent thus can be diluted to the desired concentration at satisfactory accuracy.
However, in the reagent preparing apparatus described in Japanese Laid-Open Patent Publication No. H1-167660, since the concentrated solution is supplied from the liquid amount measurement tube and the pure water is supplied from the liquid amount measurement tank different from the liquid amount measurement tube, the concentrated solution becomes difficult to be diluted to the desired concentration at satisfactory accuracy due to the liquid amount measurement error caused by the assembly error and the like which occur in the tube and the tank.
In the reagent preparing apparatus described in U.S. Pat. No. 5,800,056, the reagent approaches the desired concentration by supplying the pure water from the pump to the reagent preparing tank by a small amount at a time, and thus the high concentration reagent can be diluted to the desired concentration at satisfactory accuracy. However, the preparing operation of the reagent becomes complicating, because the pure water needs to be repeatedly and continuously supplied from the pump to the reagent preparing tank by a small amount at a time until the reagent in the reagent preparing tank reaches the desired concentration. A reagent preparing apparatus capable of preparing the desired reagent at satisfactory accuracy with a simple operation is desired.